Table 3. Distribution of antimicrobial MICs among 22 E. faecium, 22 E. faecalis, 3 E. hirae, and 2 E. gallinarum isolates from broiler chickens suffering lameness.

CLSI subclass	Antimicrobials	Species	MIC50	MIC90	Resistance (%)	Total resistance (%)	Number of strains with MIC (µg/mL)*
							0.25	0.5	1	2	4	8	16	32	64	128	256	512	1,024	2,048	> 2,048
Penicillins	AMP	E. faecium	1	4	1 (4.6)	1 (2.0)			18	1	2		1
		E. faecalis	1	1	0 (0.0)				22
		E. hirae	1	2	0 (0.0)				2	1
		E. gallinarum	1	1	0 (0.0)				2
Phenicols	CHL	E. faecium	8	> 32	3 (13.6)	7 (14.3)						18	1	3
		E. faecalis	8	> 32	3 (13.6)							13	6	3
		E. hirae	8	> 32	1 (33.3)							2		1
		E. gallinarum	8	8	0 (0.0)							2
	FFN	E. faecium	4	> 32	3 (13.6)	4 (8.2)					18	1		3
		E. faecalis	4	8	1 (4.6)						17	4		1
		E. hirae	4	4	0 (0.0)						3
		E. gallinarum	4	4	0 (0.0)						2
Lipopeptides	DAP†	E. faecium	8	16	17 (77.3)	21 (42.9)				1	4	14	2	1
		E. faecalis	2	4	1 (4.6)				2	11	8	1
		E. hirae	2	8	1 (33.3)				1	1		1
		E. gallinarum	8	8	2 (100)							2
Macrolides	ERY	E. faecium	2	> 64	5 (22.7)	18 (36.7)			3	10	4				5
		E. faecalis	2	> 64	11 (50.0)				8	3				1	10
		E. hirae	32	> 64	2 (66.7)				1					1	1
		E. gallinarum	1	1	0 (0.0)				2
Aminoglycosides	GEN	E. faecium	128	128	1 (4.6)	3 (6.1)										20	1				1
		E. faecalis	128	128	1 (4.6)											21				1
		E. hirae	128	1,024	1 (33.3)											2			1
		E. gallinarum	128	128	0 (0.0)											2
	KAN	E. faecium	128	1,024	3 (13.6)	10 (20.4)										15	4		1		2
		E. faecalis	128	> 2,048	6 (27.3)											16				1	5
		E. hirae	128	> 2,048	1 (33.3)											2					1
		E. gallinarum	128	128	0 (0.0)											2
	STR	E. faecium	128	128	2 (9.1)	11 (22.4)										20				1	1
		E. faecalis	128	> 2,048	8 (36.4)											14					8
		E. hirae	128	> 2,048	1 (33.3)											2					1
		E. gallinarum	128	128	0 (0.0)											2
Fluoroquinolone	CIP	E. faecium	4	> 16	22 (100)	36 (73.5)					11	7	4
		E. faecalis	4	> 16	12 (54.6)					10	2		10
		E. hirae	16	> 16	2 (66.7)			1					2
		E. gallinarum	1	2	0 (0.0)				1	1
Oxazolidinones	LZD	E. faecium	4	4	0 (0.0)	0 (0.0)				7	15
		E. faecalis	2	4	0 (0.0)					16	6
		E. hirae	2	4	0 (0.0)					2	1
		E. gallinarum	4	4	0 (0.0)						2
Streptogramins	SYN	E. faecium	2	4	5 (22.7)	27 (55.1)			9	8	3	2
		E. faecalis	8	16	21 (95.5)					1	2	16	3
		E. hirae	2	4	1 (33.3)					2	1
		E. gallinarum	2	2	0 (0.0)					2
Glycylcyclines	TGC‡	E. faecium	1	4	22 (100.0)	49 (100.0)		5	14	3
		E. faecalis	2	16	22 (100.0)			1	7	14
		E. hirae	0.5	4	3 (100.0)			2	1
		E. gallinarum	1	2	2 (100.0)				2
Tetracyclines	TET	E. faecium	2	> 128	7 (31.8)	24 (49.0)				14	1			1	1	5
		E. faecalis	64	128	14 (63.8)					8				1	5	8
		E. hirae	2	> 128	1 (33.3)					2						1
		E. gallinarum	64	64	2 (100.0)										2
	TYLT	E. faecium	4	> 64	5 (22.7)	16 (32.7)				9	2	6			5
		E. faecalis	4	> 64	9 (40.9)					9	4				9
		E. hirae	64	> 64	2 (66.7)					1					2
		E. gallinarum	2	2	0 (0.0)					2
Ionophore coccidiostats	SAL	E. faecium	2	4	1 (4.6)	1 (2.0)				19	1	1	1
		E. faecalis	2	4	0 (0.0)					19	3
		E. hirae	4	4	0 (0.0)					1	2
		E. gallinarum	2	2	0 (0.0)					2
Glycopeptides	VAN	E. faecium	2	2	0 (0.0)	0 (0.0)				21		1
		E. faecalis	2	2	0 (0.0)					22
		E. hirae	2	2	0 (0.0)					3
		E. gallinarum	8	8	0 (0.0)							2

MIC, minimal inhibitory concentration; CLSI, Clinical and Laboratory Standards Institute; AMP, ampicillin; CHL, chloramphenicol; FFN, florfenicol; DAP, daptomycin; ERY, erythromycin; GEN, gentamicin; KAN, kanamycin; STR, streptomycin; CIP, ciprofloxacin; LZD, linezolid; SYN, quinupristin/dalfopristin; TGC, tigecycline; TET, tetracycline; TYLT, tylosin; SAL, salinomycin; VAN, vancomycin.

^*Solid and dashed lines indicate the breakpoints of intermediate and complete resistance established by CLSI, respectively; ^†The susceptibility breakpoint has only been established for daptomycin (≤ 4 µg/mL). In this study, isolates with an MIC ≥ 8 µg/mL were classified as resistant; ^‡The susceptibility breakpoint has only been established for tigecycline (≤ 0.25 µg/mL). In this study, isolates with an MIC ≥ 0.5 µg/mL were classified as resistant.